Once they launched a [nation omitted] guy into orbit with
three pigs. After a few orbits around the Earth, a certain bell rings. The
pigs open up a compartment, take out an envelope, unwrap it, find instructions
inside, and start doing as they read: reprogram the ship's computer, adjust
the orbit, check the scientific instruments etc.

Few orbits later, the same happens - they open up a compartment,
take out another envelope, read the instructions, do as it says: reprogram
the computer, adjust the orbit, check the instruments etc.

The guy starts wondering - like, who's the boss around here?
Who's the more advanced life form?

Next time the bell rang, he jumps to the compartment, opens
the envelope, and the instructions read:

"This is for you, Mike: feed the pigs and
don't touch anything"

Now why is this a programming
joke?

It is not a joke, but rather a dream. Imagine you
had an installation procedure which basically told the user to feed the pigs
and touch nothing... back in 1994 it was a dream, and our attempt of making
it true was in a procedure named FTPADTA.